In the jazz of the 1960s, Eric Dolphy was an original: a hero to some, but also a mystery, a virtuosic improviser searching for ways of expression outside of common practice. He died of an undiagnosed diabetic condition in Berlin in June 1964, at 36, old enough to consolidate his experience and wisdom but perhaps too young to settle his reputation, which had by then taken some knocks from those who found his music abstract or abrasive.

Though he had recorded a fair amount, especially in his last four years, culminating in the 1964 album “Out to Lunch!” and a Dutch performance recorded 27 days before his death and released as “Last Date,” there is still more to be known about what produced and drove him. Right now, a half-century after his death, might be a significant turning point. His musical papers have just been acquired by the Music Division of the Library of Congress, and his music, including pieces never performed before, will be played at a two-day festival in his honor, called Eric Dolphy: Freedom of Sound, this weekend in Montclair, N.J.

The papers were long in the possession of Dolphy’s close friends the composer Hale Smith, who died in 2009, and his wife, Juanita, who later gave them to the flutist and composer James Newton. The cache, five boxes of material, is available to scholars in the Library of Congress Performing Arts Reading Room. It includes several previously unperformed works, as well as extensions or alternative arrangements of Dolphy pieces, including “Hat and Beard,” “Gazzelloni” and “The Prophet.”

It also holds a key to how he thought and what he practiced: his transcriptions of other music, including bits of Charlie Parker and Stravinsky; Bach’s Partita in A minor for flute; and a bass-clarinet arrangement for Bach’s Cello Suite No. 1. There are also many scales of Dolphy’s own devising, which he was using as the basis for improvisation; practice books and lead sheets; and a page of transcriptions of bird calls.

“The thing that really astounded me,” Mr. Newton said recently, “was that this was a person who thought very profoundly about the organization of his music.” Dolphy wrote out hundreds of his altered or “synthetic” scales. In some cases, including on the individual parts for “Out to Lunch!,” he wrote out the unusual scales beneath the composition, as a possible basis for improvisation.

“Eric was developing multiple styles of music simultaneously,” Mr. Newton continued. “There was this highly chromatic post-bop; then music that combined elements of jazz and contemporary classical; and jazz combined with world music.” (Dolphy, along with his friend John Coltrane, was listening to Hindustani music and the songs of the so-called Pygmy peoples of Central Africa.)

The festival, organized by the drummer Pheeroan akLaff and produced by his nonprofit organization, Seed Artists, will be held this Friday and Saturday at Montclair State University. It will include some of those previously unperformed works, which Mr. Newton is reasonably sure come from the end of Dolphy’s life. It will also include other Dolphy-related music performed by several generations of musicians, including Andrew Cyrille, Henry Threadgill, Don Byron, Vernon Reid, Oliver Lake, Marty Ehrlich, David Virelles, James Brandon Lewis and Dolphy’s former bandmate the 84-year old bassist Richard Davis.

Dolphy, born in 1928, played alto saxophone, bass clarinet and flute. He grew up in Los Angeles and didn’t move to New York until the age of 30 — not the standard narrative of most great figures in jazz during that time. He was an only child, and a prodigy: While still in junior high, he won a two-year scholarship to study at the music school of the University of Southern California, and his parents built him a music studio behind the house.

Dolphy came into a compositional style that used wide interval jumps in various ways, sensuous or fractured. He also organized an original improvising language, both in and out of traditional Western harmony and jazz convention. He was influenced by, among others, Parker, Art Tatum and Arnold Schoenberg, as well as the microtones and quick-pivoting phrasing of bird song.

“In my own playing,” he told the critic Martin Williams in 1960, “I am trying to incorporate what I hear. I hear other resolutions on the basic harmonic patterns, and I try to use them. And I try to get the instrument to more or less speak — everybody does.”

Toward the end of his life, Dolphy wasn’t getting enough work playing his own music. He’d been derided in the jazz press, especially after touring with Coltrane in 1961 and 1962. “He was getting criticized even by friends,” Ms. Smith said.

He left New York for Europe in early 1964, to tour with Charles Mingus. (He eventually quit that tour, determined to work on his own in Europe and to settle down with his fiancée, the dancer Joyce Mordecai, who was living in Paris.) Before leaving, he dropped off his papers and other things, including tapes and a reel-to-reel recorder, with the Smiths. The tapes yielded “Other Aspects,” an album released in 1987. But the sheet music, finally given to Mr. Newton in 2004, took a while longer to be sorted out.

Among the never previously performed pieces scheduled for the weekend are an untitled solo bass-clarinet work, to be played by Mr. Byron; a short piece for flute and bass, “To Tonio, Dead”; and “Song F.T.R.H.” and “On the Rocks,” for jazz ensembles.

Those last two were written without tempo markings, but Mr. Newton and Mr. akLaff agree that they are to be played slowly. Mr. akLaff said the pieces could be described as ceremonial music, having a “deep, dark grandeur.” (Dolphy seemed to like word puzzles; we don’t know what F.T.R.H. stands for, nor the meaning of words written in pencil on one version of the score: “Split clock birds drink wood’s angel through longhouse.”)

If Dolphy didn’t have enough cultural capital at his death to inspire a school of imitators, he became a model for how to be dedicated and curious. Mr. Lewis, 30, a saxophonist who will perform in an ensemble on Saturday, said that Dolphy suggests “a figure determined to say what he had to say at the highest level in which he had to say it.” (Like everyone who talks about Dolphy, at a certain point Mr. Lewis just had to indicate an example and listen, agog: He specified Dolphy’s bass-clarinet solo on Billy Strayhorn’s “Take the A Train,” live with Mingus in 1964, which can be easily found on YouTube. )

“He’s just amazing,” Mr. Lewis added. “He sounds completely different than anyone else on stage, but he sounds confident.”

A version of this article appears in print on , on Page C1 of the New York edition with the headline: Jazz Enigma of the ’60s Has an Encore. Order Reprints | Today’s Paper | Subscribe